Apparatus for producing tone effects in wireless telegraphy.



Patented Mar. 25, 1913.

M. BASTHAM.

APPARATUS FOR PRODUCING TONE EFFECTS IN WIRELESS TBLEGRAPHY.

APPLICATION FILED SEPT'.20,1911.

UNITED STATES PATENT OFFICE.

MELV'ILLE EASTHAM, OF CAMBRIDGE, MASSACITUSETTS, ASSIGNOR TO 'CLAIPP- EASTHAM COMPANY, OF CAMBRIDGE, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

"APPARATUSFOR PRODUCING TONE 'EEEc'rs IN 'wIEELEss TELEGBAPHY.

To all whom it may concern:

y for Producing Be it known that I, MELvrLL EAs'rHAM,

,a citizenof the United States, and resident oi Cambridge,- in the county of Middlesex and State of Massachusetts, have invented newand useful Improvements in Apparatus Tone Effects in WVireless Te- I legra phy, of'which thp following is a speci-' My invention relatesto' wireless teleg- "raphy and consists .in' an apparatus for producing regulable tone effects in the opploying' generating apparatus of ordinary commercial frequency .and securing the 'ec 0nomy, advantage and efiiciency due to the use ofgs'uch generators. To eliminate the necess ity for accurate tuning by effective damping of spark-oscillations. To adjust .2- practicable acoustic limits, particularly to regulatethe tone-pitch to suit the peculiarithe toneto any pitchdesired. within the '7 ties andlimitationsof telephonic receivers.

noiseless Myinvention is characterized by the pro- To. employ low potentials (as "contrasted :with those .which have prevailed. in the op eration of wireless telegraphic circuits) by utiliz'ing the acoustic etliciency of compara tively faint mgular musical tones, as contrasted with unmusical irregular crepltati ons,vand thus to facilitate the nsulation of condensers and antennae. To render the operation of wireless apparatus practically duction of a train-discharge, and by breaking the normal continuity of the train into recurrent train-groups, separated by inter- .vals of no discharge, and determining the or. mo

frequenc of recurrence of theseptraingroupsi hen producing a tone efi'ect- 1n correspondence to the train-group frequency,

. y and therefore independentj'of the generator frequency The tone prod'u Specification ofi-etters Patent. Application filed September 20, 1911. s rial no} 65o,39s.

themselves).

is? the" simple tone' when corresponds to the frequency of re- 'fciirrencefof' the group oftrains an d i s not" ."s ensibl perceptibly at least- -affcted ihfied by the generator cycl'undulaf or byany super'positions'of disturb- Patented Mar.25, 1913.

ing overtones or crepitations (by the trains I My invention may advantageously be practised with. anapparatus such as'illustrated in the drawings hereto annexed, in which, i

Figure 1 diagrammatically. represents parts of a wireless telegraphic circuit and shows aform of my novel spark gap device, in sideelevation; Fig. '2 shows in die m details of the spark gap devices; F 1g. 3

shows in diagram certain details of the said devices; and Fig. 4 shows a portion of a spark gap device. 7 I The operationof this apparatus is according to a IIIBthOd WhlClj forms thesubject matter of an application for patent filed by 'me concurrently herewith, Serial No. 650,452.

Referring to Fig.1: G represents. an al-' ternating current generator set which includesthe step up transformer T. The cv- 7F cle-frequencyof the generator is preferably that of the usual commercial type and practice, say, 60. The circuit which is excited bythe transformer T also; as usual, comprises thewires 1 and 2, capacity K, inductanceT' and a spark gap device, comprehensively designated .by S. The frequency of thegeneratorG is immaterial, except that for economy and convenienceit should be low. Indeed the circuit which comprises 8- the spark gap S may beeircited by a constantpotential generator. The spark gap device 18 is herein represented by two disks A and B 'B being mounted on the shaft C to rotate the bearing D,.driven by the pulley P from any suitable source gipower; the disk A being mounted in the insulating plate'E. Adjustment of the two disks A and B is' provided forby securing the pulley I to the shaft C by 'means'of a set screw 06 g" so that the face of the pulley maybe adjusted to bear on the endof the housing D and secure any desired spacing of thedisk B from the disk A. The 'face may. beheld against the housing by some simple'means, as by leading the driving belt (not shown) from 'thepulley P at a slight angle. The housing D is extended to form a boxto in close the disks A and B, the core' E. of insulating material, being secured as shown. 106

The plate A, mounted in the core plate E, 'maybe provided with external fins or plates F, for heat-radiating purposes. The two disks provide the spark gap in the circuit. The opposed faces of the disks A and B are circular. Each is inilled to form salient sectors on the disk A. and I) on th disk B (see Figs. 3 and i). The sides of these sectors are not truly radial. but are inclined to the radius by such an angle that.\vhen in the rotation of the disk B a sector I) is symmetrically opposite the interval. between two sectorso on the disk A, that is to say. is just midway between the two sectors 0, the edges of the sector 6 shall be parallel to the edges of the respectively adjacent sectors (1.

and dist-ant therefrom by slightly more than the extreme. sparking distance. The relation between-the disks and their sectors is shown-in diagram" in Fig. 3. where the outline of the developed edge of disk A is shown in'dotted lines. The opposed parallel faces of the sectors a and are brought close together by adpastinent of the disk B so that t-he .distance between them, fmeasured parallel to the axis of the disksshall be very small. say from four to eightthousandths of an inch. The two'members A and B of the spark gap devices. ortrain interrupter, are composed of highly heat-conductive material such as silver oi copper. and'are connected-in circuit'as indicated in Fig. 1. The circumferential-arc subtended by a sector a or b is'less than that'subtended by an interval ('a' or b) between two salient sectors, preferably about three fifths thereof. By making the two members A and B alike. an ample extent of surface is provided and arc-formation effectively restrained.

By'adjusting the surfaces of theopposed salient sectors-(land b so that they are but slightly separated, a spark may be established between them at relatively low po-- tentials.

The operation of the apparatus 'is a follows: Assuming that a 60 cycle generator is employed the rotaryseetor-disk B is rotated at such speed that each salient sector -b passes an opposite sector a with high frequency as contrasted with the generator-frequency, say 600 times a second. The estab-- lislnnent'and interruption of spark communication' thus will produce-say 600 isolated train-groups per second.. I f the circuit is,

. for instance, adapted to charge the concauses effective damping of oscillations, so

clea r musical tone of high acoustic elliciency,

determined as to. pitch by the train group frequency at the sending station: above ticscribed. The shape of the'salient sectors a a'nd b. above described. insures such scparation along the entire length of each sector'- edgeas will produce spark discharge interruptions without fail. As the approaching edges of sectors on the two disks are approximately parallel when sparking distance is reached.-there will he no leading point where discharge will he predetermined. therefore the whole heat-conductive mass of each sector is efiicient to preventvaporization of metal and the formation of an are, which is not only destructive of apparatus but interferes with the quick quenching of spark-oscillations.

The train-groups produced by the above described apparatus according to my method, will be established at that point where the potential attains sparking intensity. and will be discontinued when in the decline of the electromotive-force the potential falls' below the sparking-intensity. Theoretically-thereforethere' will be interruptions in the regular continuity of the train group series, and electrically speaking this discontinuity must exist. Aocoustically'; however. no such discontinuity is perceptible. It might be snpposed that the recurrence of maxima in synchrony with the generator cycle would produce an undertone, but .so far as I have observed this does not occur.

The high heat-conductivity and relatively large mass of the sector-disks and the metal part of the housing will sufiice, in apparatus of moderate capacity, to control temperatures. 'It is'advantageous to have the housing of these disks closed, since constant circulation of fresh bodies of air tends to 0x1- 'dize the metal surfaces and thus deteriorate their efiiciency. Complete closure of the housing also suppresses the noise of the sparking devices and quiet-s the operation of the apparatus.

\Vhat I claim and desire to secure by Let-, ters Patent is:

1. In a spark ga as for wireless telegraphicap'paratus, t eeombination' of relatively revoluble conductive members, armed with salient se merits, the surfaces of revolution of the aces of the segments of the two members being equidistant at all points.

2. In a spark ga as for wireless telegraphic apparatus, t e combination .pf-relatively revoluble conductive members, armed with. salient segments, the surfaces of revolution of the faces of the segments of the twomembers being equidistant at all points and the angularlntervals between the salient segments of one member bein substantially greater than the angle subtended by the segments 'of the' other.

' 3. In a spark gap; as for wireless 'telegraphic apparatus, the combination of two similar relatively revoluble parallel conductive disks, each armed with salient segments, the intervals between the segments subtending anglesof revolution greater than, those subtended by the segments.

4. In a spark gap, as for Wireless telegraphic apparatus, the combination of two similar relatively revoluble parallel conduc' t-ive disks, each armed with salient seg ments, the intervals between the segments 20 approximately parallel whena segment of 25 onedisk 1s symmetrically opposite an interval between segments on the other disk.

Signed by me at Boston, Massachusetts,

this eighth day of September 1911.

, MELVILLE EASTHAM.

lVitIlesses .CHARLES D. \Voonnnnur, ODIN ROBERTS. 

